Serum leptin levels in patients with primary hyperaldosteronism before and after treatment: relationships to insulin sensitivity.

BACKGROUND

Leptin is a protein hormone produced predominantly by adipocytes that plays a role in food intake regulation and a series of other physiological processes including blood pressure regulation.

OBJECTIVES

The aim of our study was to compare serum leptin levels in patients with primary hyperaldosteronism (PA) with those of healthy subjects and to explore the relationship of serum leptin levels and the parameters of insulin action in these patients before and after surgical or pharmacological treatment.

METHODS

Serum potassium, leptin, aldosterone, insulin levels and plasma renin activity were measured and hyperinsulinaemic euglycaemic clamp was performed in 11 patients with PA and 11 healthy age-, gender- and body mass index (BMI)-matched subjects. In eight of 11 patients the same measurements were repeated at least 6 months after surgical or pharmacological treatment.

RESULTS

The basal serum leptin levels in PA patients did not significantly differ from those of healthy subjects (mean+/-s.e.m. 8.4+/-1.9 vs 11.2+/-1.8 ng/ml, P=0.30), although their insulin sensitivity was significantly impaired (PA patients vs control subjects: glucose disposal rate in the last 20 min of clamp (M) 18.7+/-1.8 vs 30.6+/-3.3 micromol/kg/min, metabolic clearance rate of glucose (MCR(g)) 3.9+/-0.5 vs 7.2+/-1.1 ml/kg/min, P<0.05). The surgical or pharmacological treatment of PA patients increased significantly their serum leptin levels (10.9+/-3.7 vs 8.4+/-1.9 ng/ml, P<0.05) and simultaneously improved their insulin sensitivity. Basal serum leptin levels in both groups correlated positively with BMI and serum insulin levels. The inverse relationship between serum leptin levels and the insulin sensitivity parameters was found in both PA patients before treatment and healthy subjects. These relationships disappeared after treatment of PA patients except for those between serum leptin levels and MCR(g).

CONCLUSION

Basal serum leptin levels in untreated patients with PA do not significantly differ from those of healthy subjects, but increase significantly after surgical or pharmacological treatment. The increase in serum leptin levels is paradoxically accompanied by the improvement of insulin sensitivity in these patients.